There had been war between the Aws and the Khazraj during the days of ignorance. One day, while they were sitting together, they brought up what had passed between them until they grew angry, and they rose against one another with weapons. Then this was revealed, "And how could you disbelieve while the verses of Allah are being recited to you and His Messenger is among you?" [Al Imran 3:101].
كانت بين الأوس والخزرج حرب في الجاهلية، فبينما هم يوما جلوسا إذ ذكروا ما بينهم حتى غضبوا، فقام بعضهم إلى بعض بالسلاح، فنزلت: {وكيف تكفرون وأنتم تتلى عليكم ءايت الله وفيكم رسوله}.
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Ibn Abu Hatim narrated it in his Tafsir (3/720) from Husayn bin Sakan, who said, Abu Zayd Nahwi told us, Qays bin Rabi informed us, from Aghar bin Sabbah, from Khalifa bin Husayn, from Abu Nasr, from Ibn Abbas, and he mentioned it.Its chain is hasan. Qays bin Rabi is predominantly considered daif, because his son introduced material into his narrations that was not originally part of his hadith, and he then narrated it as such. However, Tabarani narrated it in Al-Kabir (12/99) through another route, from Sufyan Thawri, from Aghar, in a similar manner. So it appears that Qays bin Rabi did not err in this particular hadith.